diff --git a/src/parser/actions.pm b/src/parser/actions.pm
index 6fc836107db..60fae823495 100644
--- a/src/parser/actions.pm
+++ b/src/parser/actions.pm
@@ -1062,9 +1062,21 @@ method type_constraint($/) {
     if $<fulltypename> {
         $past := $<fulltypename>.ast;
     }
-    else {
+    elsif $<EXPR> {
         $past := make_anon_subtype($<EXPR>.ast);
     }
+    else {
+        my $value := $<value>.ast;
+        $past := PAST::Op.new(
+            :name('infix:,'),
+            PAST::Op.new(
+                :pasttype('callmethod'),
+                :name('WHAT'),
+                $value
+            ),
+            make_anon_subtype($value)
+        );
+    }
     make $past;
 }
 
diff --git a/src/parser/grammar.pg b/src/parser/grammar.pg
index 80e16f35059..bb9543ba2e0 100644
--- a/src/parser/grammar.pg
+++ b/src/parser/grammar.pg
@@ -502,9 +502,9 @@ rule type_declarator {
     {*}
 }
 
-# XXX STD.pm also has value in here?
 rule type_constraint {
     [
+    | <value>
     | <fulltypename>
     | where <EXPR: 'm='>               # XXX <EXPR(item %chaining)>
     ]